<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <script>
         //在运行的时候，JS引擎会根据右边的值，进行类型的推导
         var num=100;
         var name="张三";
         num="李四";
         console.log(num);
    </script>
</head>
<body>
    
</body>
</html>